slicer apprixmation for 3d print
It may not be 100% accurate but the Remesh modifier could give you a idea of what the 3D printed object would look like.



To get the voxeled style, choose Blocks from the Mode menu.

To get the right size I would add a voxel-sized cube (whose dimension can easily controlled in the Properties panel) as reference, then tweak the modifier's parameters (start from the the Octree depth and than refine with the Scale) till the subdivision are about the same size of the reference cube.



Warning: if you alter the object's bounding box size, you must re-eyeball the subdivision rate.